Corneal laser surgery requires moving and focusing (i.e. steering) a laser beam to a succession of many predetermined focal points. Depending on the particular surgical procedure that is to be performed, these predetermined focal points may be either on or within a medium (target tissue). In either case, the intended purpose is to photoalter target tissue in accordance with a predetermined pattern. In refractive surgery, for example, the target tissue is normally stromal tissue in the cornea of a human eye, and the steering of the laser beam is accomplished by the moving, tilting or realigning of optical components (i.e. lenses and mirrors) of the laser system.
Laser surgery systems that are currently being used typically include a dual-mirror combination that is manipulated to move and direct the laser beam as the beam transits the system. Within this combination, one mirror is moved to effect movements of the laser beam's focal point in an x-direction on an x-y plane in the target tissue. The other mirror is then moved to effect movements of the focal point in a y-direction on the x-y plane in the target tissue. The result here is that for each of these movements, the laser beam will necessarily be directed away from a central path through the system. Moreover, these effects are cumulative. Thus, it will happen that as the laser beam is moved to effectuate “x” and “y” movements for a particular laser surgical pattern, the center of the beam path will be moved away from the center of downstream optical components in the system. At some point, the combined effects of these movements can significantly reduce the optical efficiency and the surgical precision of the laser system.
In light of the above, it is an object of the present invention to provide a device for steering a laser beam to a focal point in a medium during laser surgery wherein movements of the laser beam are compensated to maintain the beam substantially centered on the optical components of the system as the beam transits the system. Yet another object of the present invention is to provide a device for steering a laser beam to a focal point in a medium during corneal laser surgery wherein displacements of the laser beam, from the center of optical elements, are minimized during “x”, “y” and “z” movements of the laser beam's focal point in a target tissue. Still another object of the present invention is to provide a device for steering a laser beam to a focal point in a medium during corneal laser surgery that is easy to use, relatively simple to manufacture, and comparatively cost effective.